Synchronizer for indicators



Jan. 4, 1955 s. N. VAN VOORHIS 2,698,931

SYNCHRONIZER FOR INDICATORS Filed May 9, 1945 F|G.l,

19 DUPLEXER MODULATOR J T AMPLlFlER MIXER PU LSE TRANS- MITTER MU LTI VIBRATOR I RECEIVER l8 27 TRIGGER FMorAM l l6 /28 29 SWEEP GENERATOR ZI/ 22 PULSE M TRANS- J MITTER 3: 32 33 36 37 3a FM or AM SEPARATOR SY NCHRO- MOTOR POTENTIO- RECEIVER i} NIZER METER SWEEP GENERATOR 44') 45) 467 47) 480w JBEN FREQUENCY BLOCKING MULTI VIBRATOR DIV IDER OSCILLATOR VIBRATOR 37 5| 50 497 487 MOTOR A P 20 PHASE Rc M SELSYN SPLITTER FILTER INVENTOR.

STANLEY N. VAN VOORHIS AT TOR NEY United States Patent SYNCHRONIZER FOR INDICATORS Stanley N. Van Voorhis, Rochester, N. Y., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application May 9, 1945, Serial No. 592,794

4 Claims. (Cl. 343-6) This invention relates to a means for displaying at a second cathode ray tube the data appearing on a first cathode ray tube which is remotely separated from the second cathode ray tube.

A system of this character is highly applicable to military operations, particularly naval operations. For instance, a scouting plane bearing radio echo apparatus can be employed to keep the carrier ship informed of obstacles normally out of the range limit of shipborne detection apparatus. It has been found that for a most comprehensive record of remote obstacles, Plan Position Indicating apparatus is most advantageously used herein. This type of radio echo gear consists primarily of a rotating antenna transmitting a highly directive energy beam in phase correspondence with a rotating radial sweep on a cathode ray tube. In accordance with the principles of this type of apparatus the angular displacement of the sweep with respect to a given reference line corresponds to the orientation of the antenna and therefore indicates obstacle bearing, While the distance along the sweep line from the starting point, i. e. the center of the cathode ray tube, is taken to represent range. 1

It is therefore an object of this invention to provide a means for transmitting the data appearing on one cathode ray tube to a second cathode ray tube.

It is another object of this invention to provide a means 7 for synchronizing the electron beam sweeps of two cathode ray tubes remotely separated from each other.

It is another object of this invention to provide a means for synchronizing both the production and the rotation of radial beam sweeps of two cathode ray tubes remotely separated from each other.

Other objects and features will become apparent upon a careful consideration of the following detailed description when taken together with the accompanying drawings the figures of which are designed for the express purpose of illustration and are not to be taken as a definition of the limits of the invention. Reference for the latter purpose is to be had to the appended claims.

Fig. l is a block diagram of the transmitting station wherein the original data is recorded onthe first cathode ray tube.

Fig. 2 is a block diagram of the receiving station wherein the second cathode ray tube is located, and

Fig. 3 is a block diagram illustrating in greater detail typical embodiments of the synchronizer shown in Fig. 2.

The present invention, for purposes of avoiding confusion, is described as applied between aircraft and ship. It must be understood, however, that the invention will function equally well between ship and shore, ship and ship, or aircraft and shore. specification and claims when the word craft is used, it is meant to embrace both air and naval craft.

Reference is had more particularly to Fig. 1 wherein there is shown a typical embodiment of the-present invention as employed at the transmitting station of the y system herein described for displaying the data appearing on one cathode ray tube at a second cathode ray tube remotely separated from the first cathode ray tube. There is included at the transmitting station, for purposes of obtaining range data on the first cathode ray tube, a radio echo detection system of the type hereinbefore outlined comprising a pulse transmitter 18 coupled, for example, to a suitable dipole antenna It} by way of a low-loss transmission line 19, and through an electrical rotary point,

Hence, hereinafter in the 0 that produced by the trigger signals.

, apparent to those skilled in the ar-t that various other arsuch as a pair of slip rings. The output of the pulse trans- Patentecl Jan. 4, 1955 found that optimum operation of the system is obtained with the antenna rotational speed set at approximately 20 R. P. M.

There is also coupled to the antenna shaft 14 a trigger circuit 15 for use in keying the pulse transmitter 18 and also as a means for maintaining a systematic relation between antenna rotation and the pulse repetition rate of transmitter 18. For instance, 480 pulse per second output from transmitter 18 has often been used with the above selected antenna speed of 20 R. P. M. which indicates a 1440:l step up between antenna speed and pulse output. The trigger circuit may comprise, for example, a toothed wheel geared to the antenna shaft 14 (the required step up gear ratio being used) arranged to cut a magnetic field having a winding associated therewith so as to induce a voltage pulse in the winding for each interruption of the field by the toothed wheel. The output of the trigger circuit 15 is fed into a pulse shaping amplifier 16 and into a modulator 17 for keying the transmitter 18.

The output of the trigger circuit 15 is also coupled to a saw-tooth generator 21 for producing a linear sweep 28 of the electron beam of cathode ray tube 22 each time the transmitter 18 is fired and in synchronism therewith. In accordance with the principles of radio echo systems, a receiver 27 is coupled to the antenna 16 by way of a duplexing device 26 which is now known to the art and enables transmission and reception to be carried on from a single antenna. Thus energy reflections caused by the transmitted pulse striking remote objects, are received by antenna 10, amplified by receiver 27 and applied to the beam sweep of cathode ray tube 22. As a consequence an observer will see on the sweep 28 of cathode ray tube 22 an indication of the transmitted pulse followed by a series of energy reflections, provided that there are present within the path of the transmitted pulse obstacles capable of producing reflections.

Ways, for example, a sine wave potentiometer 23 may be geared to theantenna drive gear 13 to produce a pair of quadrature sine waves for modulating the saw-tooth output of generator 21. Or if the cathode ray tube 22 is of the magnetic yoke deflection type the magnetic yoke I may be geared to the antenna.

In transmitting the data appearing on the cathode ray tube 22 the output from the pulse shaping amplifier 16 is fed into a mixer 24 to modulate an F. M. or A. M. carrier wave emitted at antenna 29 by the F. M. or A. M. transmitter 25. Also applied to the mixer 24 for purposes of modulating the carrier output of transmitter 25, is the video output of receiver 27. Thus each trigger pulseand the ensuing energy reflections caused by the respective transmitted pulse from transmitter 18, is therefore radiated from antenna 29 in the proper time phase.

As will become more apparent in connection with the description below of the operation of the remote cathode ray tube unit, it is desirable to be able to separate. there the trigger signals and theenergy reflection signals. Ac-

cordingly it is advantageous that the modulation produced mixer 24 that the maximum deviation which may be pro-' duced by the video signals is limited to a value less than It will at once be :gaaaam rangements may be employed equally well to permit the *later separation of the-two signals.

At the receiving statiomqshown in Fig. 2, the second cathode ray tube 35 is located, remotely separated from itheifirstcathode ray: tube;.22,.and-on. which itsis desired to record thexdataappearing on .thefi'rst cathode raytube.

:Eixedat the receiving station is;.an OIZ AtLM. '=receiver 32, depending-Ion the type-.communicatiorr;trans- 1nitter :25.-,nsed atzthe .transmitting statiornscoupleds to itheantenna 31 .for use in amplifying; and :detectingzithe .itrigger pulse and video signals emitted by .the; transmitter 225;-in; Big. 1. The .detected :output .of ;the receiver? 32 is fedt into a separator 33 for 'usein:separating,theztrigger :pulses r from 1 :the video J: signals, and :'may "comprise, tin gthezspecific embodimentmentioned above, a;pair-;of ithermionic vacuum tubes having their inputs connected:l;.in ipar'allel, .cne of :the tubes :being biased vto:cut-otfzsoilthat only thezhigbamplitude triggerpulses arerpassed While :the othenzmay bebiased for classuAroperationto pass both "trigger pulses and: videoasignals. .Otherccombinations of :degree ,or type of-zmodulation .at: the transmitter -will erequire :theappropriate arrangement of ithetseparator :circuit. :The trigger output from the separator.33.asrtaken .i'lrom lead :42' is used toaliey theysweeprgenerator 334 and .frhereby initiate thezradialssweep, for;example28 ;onsthe :catliode:.ray tube 35,'-while'-thevvideo outputxrfromnthe =separator 33'as taken from lead 41 -is;also. appliedrto athe :cathode ray tube 35. Thus oneach: sweep line there :will appear. an indication of the trigger. pulse ,followed by its -respective -video signalsain thexpropentime phase.

In. ;accordance: .with another: feature of Ethe invention, sweep 28'. of cathode ray tube: 351is 'to'w-be rotated;;in:syn- :chrohismwith sweep 28'of;the cathode; ray tuber22. T his :wrnay abe accomplished byputilizing. a POIJEiCIliOf the trigger :output from separator 33; as :taken from-lead- 425and apply it to :the synchronizer; 36'; the-elements, of=which=are shown ein bl oclein. Fig. -.3= "which is to be described hereinafter. The synchronizerj36.functions :tO .produce,- for example, 8n60. cycle voltageby frequency =division;of:;the 480, cycle zxtrigger' pulse;E ands; applied v,to: the motor ;-37. Motorv-.37

sis; geared through BKPI'OPQlf-lYChOSfiI]; gears-combination to a sine 'wave potentiometenSS, for instance; to produce: a :twenty cycle per --minute:voltage--output ;ther efromrin' ac- ,ICOl'dfil'lCC with :the selected rotational -speedof the;antenna :10: and sweep line 28 at the transmitter station shown in r-Fig. '1. :The output from-sinewave rpotentiometers38 ,consists of a, pair of quadrature varying voltages ,used=. to ';modulate; the saw-tooth output. from, sweep;;generator3 34 and thereby cause angular movement'ofrthevsweep 28' win synchronism' withrsweep" 28. 1f,'however,,.a.-magnetic .jdeflecting yoke is used oncathoderaytubei zmoton 37 may then be gearedthrongh-the properlyehoseng-gearcom- =bination to the yoke.

Reference is now had tofFig Ci -wherein there-is. shown -a block diagram of the synchronizer36 contained-in 2. Synchronizer 36 may, for.-example compriseta .twide gate multivibrator-44 keyed bythe 480 cycleptr igger :pulse from 'the'separatorfi33. -The output of,the multivibrator" 44-isfed: into a frequency divider; 45 having-t'preferably a 4 to l division factor,-whi'ch; in rturna-keys a vblocking oscillator AG-having; a time constant set for 60 cycle operation. .The '60 cycle output;of --bloc ki ng oscillater 46 isv then applied to asecond=multivibrator ,47 which produces a 60 cycle-square wave output. {Elie-outcPUlZ-Of the second multivibrator is filtered:: by.rway ,of; a suitable R.Csfilter networlo48zto produce a .60..cycle sine wave which is. then-split= intoapa-ir, oflguadrature varying voltages by Way of phase .splitteri49. andapplied tothe stators of a twoaphaseselsynmotor 50. 's'Thesinglc phase output from the..selsynr50 as 'takenimm' the rotor is then fed into .the potentiometerdrive. motori-37sby1 way 7 of amplifier '51.

"When the transmitting station is .airbOIn ,or.-;"'sl 1ip- "borne, synchronizationgbetweenthe rotating Iadial-sweeps of the transmitter and receiver" may be' l'osb-uponrrapid turns of'the'craft, or as' a resultiof"momentaryfeiilure --of the radio transmission system, thereby causing the pat- "tern 'on the receiving cathode ray'tube to shift slightly. If-this occurs synchronization may' be restored-by rotating by hand the rotor of the selsyn 50thus changing the frequency of the applied voltage at -the-potentiometer drive motor 37. The patternwillthen drift into -position and remain there as the rotor is stopped.

Another feature of ithe -present invention swhich :is *highlyapplic'able foruse-at the transmitting station when airborne or shipborne installation is employed, is a "mansion-indicating thecourseof the-craft at the receiving station. Such a means is shown in Fig. l and comprises a cam 43, a micro-switch 52 and a multivibrator 5 53. Cam 43 is secured to the antenna shaft 14 and fixed in phase correspondence with the antenna 10, while the microswitch 52 is fixed on ,the craft in axial relation with the fore and aft axis in such a manner that each time antenna l0 -is" oriented -into' the course of the craft cam 10 43 actuates microswitch 52. .,Microswitch 52 in turn operates*multivibrator 53Lthe output of which is applied to the-mixer 24-to-modulate-the carrier wave being emitted at antenna 29.

Thereforesthewobseryer atthe receiving station will see as a course marker a'highly illuminated sweep line or a series of intense...do.ts on a sweep-line depending upon the periodicity of the multivibrator 53, and provided, of course, that intensity modulation is used at the cathode ray tube-.35. Thusqby means of radio communications the p'ilot-v of-.;thecra ftean inform the observer at the receiving astation ,of his. ,true. course which -will enable the observer at the receiving station to set the course marker .incorrespondence onuthereceiVing cathode ray tube 35 .by rotatingathertubealthereby fixing all other signals on the receiving tube, inra similar relation as those occupied by signals at :the transmitting station.

.Stilhanother feature embodied by the present invention is a-means for. measuring the distance the transmit- -,tir 1g';station -is from the receiving station. Such, a means .is shownin Fig-,2 andmay comprise a pulse transmitter .439 ,capable-ofemittinga signal which may be pickedup by,antenua .10.-and receiver "27, keyed by the trigger ,pulse-fromzzthe separator 33z-.and.-which thereby emits a *pulseqf om antenna 40. :The pulse from-antenna is picked up at the, transmitting station by antenna 10 applied to receiver. 27 :whereit is ,in .turn used to modulate ,thecanrier-swave from.-antenna 29 and subsequently received by the communications .-receiver 32- and applied to "the, cathqderaytube-35. asa video signal indicatingxdirectly 'the range of the transmittingsstation.

.iFromJhe foregoing description-it becomes obvious-that eangobserver at the receivingstation-who is aware of the range, bearing, and. course .of vthe transmitting station I has-readily availablethe information 1 required in constructing a-graphical-plot to, aid tactical operations.

AlthoughI,,have.-.shown and.described the present in- -.ventionjassappliedsto a radio echo-system, it must be understoodJhat-it will function equally. Well for any such systemwwhereinvit. is desired .to, display data appearing on one cathode ray tube to a second cathode ray tube ir- ,respective.ofthesourcefromwhich the datawas originally obtained. i'llhereforethis invention isnot to be-restricted t. except:insofanasnecessitated; by .the .prior. art or appended tjclaims.

.what; lzclaim is: .l.- A .radar.relay, systenr for presenting on a remotely located cathode ray.,tube,sear.ch data obtained-by a radar systemeincludinga transmitter of pulsed energy, a rotat- ..,ingz.antenna.. for scanning anarea' with said energy and a receiver of echo signals from targets upon which said energy-impinges,comprising, means coupled tosaid antenna producinga-tseriesvof pulses, the repetition rate of nwhichaisaspredetermined multiple of the rate of, rotaition tof;said antenna,-rneans :operable by the rotation-of nsaidtantenna periodically generating a positional signal -indicative'..ofrtheprotational:position of said antenna,- a ;mixingz-circuit,- ,-means applyingsaid series'of pulses, said rpositional-,signals:.andasaid. echo signals to said mixing ..circuit, -,a-.source of,.carrier.,energy, .said mixing circuit :beingwoupled to .said .source of carrier. energy whereby said carrier. energy; is modulated by the .output of said mixing circ,u it,.-a remotely located receiver responsive to ..;s,aid carries:energy,;,circuitrneans coupled to said remote ;receiver,separating sairhaeries of pulses-from said-echo signals r and jsaidzpositionalq signals, :Ineans' responsives'to srsaid series .of pulses-producing apair of timing waves in :pbase quadrature ,having'a" frequency which corresponds .to theirotational"rateof saidantenna, a sweep generatring;circuihoperabletoggenerate a sweep voltage for said ,r;cathode rayiubegin-responseto each of said pulses, means ,--respo,nsive to :sa'idtiming wavesproducingrotation of said --;sweepszinusynchronism -with therotation of said antenna, .and;rneansaapplyingisaid echo-signals and saidpositional =Fsign'als-to,- saidr' cathode ray tubewto presentthereon said search data and the positional relationship of said antenna thereto.

2. A radar relay system for presenting on a remotely located cathode ray tube search data obtained by a radar system including a rotating directional antenna and a receiver of echo signals, and indicating on said cathode ray tube the range and bearing of said radar system from said remote cathode ray tube, comprising means coupled to said antenna producing a series of pulses the repetition rate of which is a predetermined multiple of the rate of rotation of said antenna, means operable by the rotation of said antenna periodically generating a positional signal indicative of the rotational position of said antenna, a source of carrier energy, means modulating said carrier energy with said echo signals, said pulses and said posi tional signals, a remotely located receiver responsive to said carrier energy, means coupled to said receiver separating said pulses from said echo signals and said positional signals, means responsive to said pulses producing a radial sweep on said cathode ray tube which rotates in synchronism with said antenna, means applying said echo signals and said positional signals to said cathode ray tube to present thereon said search data and the positional relationship of said antenna thereto, a pulse transmitter responsive to said pulse transmitting pulses of a frequency capable of reception by said rotating directional antenna, the pulses thus received by said rotating antenna being r e-transmitted as an echo signal, received at said remote receiver and applied to said cath ode ray tube, thereby to indicate thereon the range and bearing of said radar system.

3. In a radar relay system for presenting on a remotely located cathode ray tube search data obtained by a radar system including a rotating antenna, apparatus for producing a rotating radial sweep on said cathode ray tube in synchronism with the rotation of said antenna comprising, means operable by said rotating antenna generating a series of pulses the repetition rate of which is a predetermined multiple of the rate of rotation of said antenna, a source of carrier energy, means for modulating said carrier energy with said pulses, a remotely located receiver responsive to said carrier energy for detecting said pulses, a frequency divider being operable to divide the frequency of said pulses by the aforesaid multiple, means operable by said pulses of divided frequency producing a pair of timing waves in phase quadrature, a synchronous motor, said motor being energized by said timing waves, a sweep generator operable by said pulses of undivided frequency producing a radial sweep on said cathode ray tube, and a sine wave potentiometer being driven by said motor and coupled to said sweep generator to rotate said radial sweep at the same speed as said rotating antenna.

4. In a radar relay system for presenting on a remotely located cathode ray tube search data obtained by a radar system including a rotating antenna, apparatus for producing a rotating radial sweep on said cathode ray tube in synchronism with the rotation of said antenna and indieating on said cathode ray tube the angular direction of said antenna at a particular instant comprising, means operable by said rotating antenna generating a series of pulses the repetition rate of which is a predetermined multiple of the rate of rotation of said antenna, a cam operated switch operably coupled to said antenna, means generating a positional signal upon the closure of said switch at a predetermined rotational position of said antenna, a source of carrier energy, means for modulating said carrier energy with said pulses and said positional signals, a remotely located receiver responsive to said carrier energy for detecting said pulses and said positional signals, means coupled to said receiver for separating said pulses from said positional signals, means responsive to said pulses producing a pair of timing waves in phase quadrature having a frequency which corresponds to the rotational rate of said antenna, a sweep generating circuit operable to generate a sweep voltage for said cathode ray tube in response to each of said pulses, means responsive to said timing waves producing rotation of said sweeps in synchronism with the rotation of said antenna, and means applying said positional signals to said cathode ray tube to present on the face thereof an indication of the rotational position of said antenna at the aforesaid particular instant.

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